Trunk-testing circuits for selector switches



Oct. 16, 1928. 1,687,669

E. E. HINRECHSEN TRUNK TESTING CIRCUITS FOR SELECTOR SWITCHES Filed April 9, 1925 tainly on the first idle trunk reached and at H Patented Oct. 16, 1928.

UNirED- STATES ra'rsur orr ca.

EnWARn E. HINRICHSEN, on NEW Yonk, N. Y; AssreivoE, BY MEsN assrenmniv'rs, r0 WESTERN ELEoTnIo COMPANY, INCORPORATED, a conronarron on NEW yomr.

TRUNK-TESTING CIRCUITS FOR s EoTon SWITCHES.

Application filed April 9, 1925 Serial No. 21,787.

This invention relates to telephone exchange systems, and more particularly to a, trunk hunting circuit for use in such tele-;

phone systems.

Trunks or lines extending from a telephone oflice to various destinations are ordinarily placed in groups according to their destination in order that they may be readily se-' lected by an operator or automatic apparatus. lVhenautomatic apparatus is used for selecting trunks, it is the usual practice to connect the trunk conductors in multiple to several groups of stationary terminals and employ a plurality of switch brushes to hunt over the stationary terminals for trunks, to a particular destination, that are idle.

It is important that selector switches operate as rapidly as possible during trunk hunting in order to make the time required for finding an idle trunk as short as possible.

It is diflicult to providea test which willstop a rapidly moving switch positively and C61 the same time prevent two switches which may test the same trunk simultaneously from becoming associated with said idle trunk. This is especially true o'l switches of the self interrupting type in which the brushes are advanced by the return stroke of the magnet armature.

Where a number of such switches are hunting over the same multiples at the same time,

' delays in makingtelephone connectionsand .requiremore apparatus than would otherwise be necessary if it were impossiblefor more than one incoming line to connect to one outgoing trunk or line.

It is an object of this invention to provide a testing means which will permit trunk hunting at high's' pecd and at the same time prevent double conections with'out the use of apparatus of more than ordinary sensitiveness for speed of operation.

A feature of t-hisinvention resides in the provision of means in each of a plurality of hunting circuits to establish an auxiliary driving circuit, efi'ective'when the hunting brushes 01 more than one switch selectterminals associated with the same idle trunk or line to prevent the connection of a plurality of incoming lines to a single outgoing trunk or line. v

A further feature of this invention resides in the provision of means to prevent the sc lection of a trunk or line whichhas a defective test circuit connected to the test terminal of a hunting switch.

This and other features of the nvention will be apparent from the following descrip- -tion,.taken in connection with the'ac'companying drawing which illustrates the tip" and ring conductors ota group of trunks or lines and the test terminals associated with such trunks connected to stationary contacts of switches. Brushes associated with these switches are rotated. under the control of a combination of apparatus to locate :idlc trunks. Two hunting s witchessand two control apparatus combinations have been shown. There may, however, be any numher in a trunk group and there may be a plurality of such trunk groups in an oflice Switches of the self-interrupting step-bystep type have been disclosed but the invention is equally applicable to any type of switch which advancesautomatically to find an idle line or trunk.

A plug and jack have been shown forthe associationof the incoming line with the may be selected by automatic apparatus such as a selector. 7

Detail clesm iptz'on.

Let it beassumed that an incoming line con- 'nected to plug 16 is to be connected to a trunk extending to a particular oflice served- :by

switch 10. An operator inserts tlie plug 16 hunting circuit. This, however, may be any i type of apparatus and the hunting apparatus brush 7. "Assuming thatbrush 7 is resting.

on terminal No. 6 which is a busy trunk char acterized by ground potential, a circuit is established to energize the windingof mags net 3 from grounded battery through said winding, leftnormalcontact of relay 1, conv tact of magnet 3, contact of relay 2,. right f relav 5.

contact of relay 4, brush 7 and its associated contact to ground. The magnet 3 is energized over the circuit traced, to propel brushes 7, 12, and 13 to the next successive terminal N o. 7. This terminal is also assumed to be connected to abusy line which again energizes magnet 3 through its self-interrupting contact. The switch brushes are thus propelled to terminal No. 8 which is connected to an idle trunk, as indicated by battery potential, through resistance 8.

Relay. 4 1s now energlzed from grounded battery through the winding of magnet 3,

leftcont-act of relay 1, contact of magnet 3, contact of. relay 2, to groundv through the winding of relay 4. r The resistance of relay 4 in the circuit traced, does not allow the mag net 3 to again operate.

It will be'noted that the operating circuit for relay 4 was established upon the operation of relay 2,'but a shunt circuit is also established to prevent the operation of relay 4' during the time that .brush r7118 associated with busy terminals so that relay 4 cannot operate until brush 7 is associated with a terminal connected to an idle trunk with the test terminal connected to battery or connected to a trunk with a "faulty test terminal, such-as an open conduc tor, between the battery and the test terminal. I

The operation of relay 4 establishes aci'rcuit to energize the windings of marginal relay5 from ground through its right and left Windings, right contact of relay 4, brush *7,

resistance 8 to grounded battery. Relay 5 operates and establishes a locking circuit for itselffrom ground, through its. left contact and leftwinding. The operation-of relay 5 further associates the incoming linewith the out-going trunk through the right outer and inner contacts of relay 5 and brushes 12 and 13' and their associated terminals. The incoming line is thus associatedwith the idle :outgoing trunk, and relay 5 remains oper-,

ated until the conversation has ceased and the trunk is released. The test terminal is made busy by its, connection to ground through the low resistance leftwinding of Let it be assumed that terminal 8 is a busy terminal, the same as'terminals Nos. 6 and 7 i and that brushes 7, 12, and 13 have been propolled to. terminal No. 9 by the operation of magnet 3, as previously described. When.

brush'7 arrived at terminal N o. 9, since the. conductor associated with this terminal is open, there is no ground to shunt relay 4 which operates as previously described over a circuit throughthe winding cit-magnet 3 to battery. The operation of relay 4 connects the windings of relay 51toterminal No. 9

through brush 7 ;-but since' the conductor con-.

nected to terminal No; 9 is open, there'is no battery potential to operate relay .5. It therefore remains in areleased condition.

to cause their release.

3 propels the brushes 7, 12, and 13 to the next With relay 5 in its normal released condition and relay 4 operated, a circuit, is established. to operate relay 1. from ground through the left back contact of relay 5, left inner contact of relay 4 to battery through thewinding of relay 1. It will be noted that p relay 1 isslow to operate in order that suf to maintain .relay 4 energized until magnet 3 has opened its contact. -This'circuitmay be traced from grounded battery, through,-

resistance 9, left outer contact of relay 4, left a contact of'relay 1, contact of magnet 3, 0on

tact of relay 2 to ground through .the wind-.1

ing of relay 4. I p v Upon .the operation ofmagnet 3, the holding circuit for relay 4 isopened to cause its;

release. Therelease of relay 4 opens the energizing circuit for magnet?) and relay l The release of magnet terminals which may be associated with a busy or idle trunk. Itwill be noted that when the switchbrush 7 is advanced to terminal No. 10,the apparatus of thehunting circuit is inthe same condition as it was when brush 7 started to hunt for an idle line. Therefore, if the tenth terminal is associated with a busy line, a circuit is established to ice energize magnet 3 to advance the brushes to p the next succeeding terminals. In this manner, the.brushes are advanced until an idle trunk isselected and the incoming line conneoted to brushes 12 and 13 by the operation of relay 5; 1

Let it be assumed thatbrushes 7 and :27 are positioned upon the trunk associated with terminal No. 6 of each switch, and that plugs 16and 36 are simultaneously inserted into jacks 17 and 37. Let it further be assumed that magnet 3. and magnet 23 are simultaneously-energized in'the manner previously described to rotate the brushes of the switches. 10 and 20 in search of an idle trunk and that brushes 7 and 27 arrive atterminal No. 8. at.

(the same time.

Since battery potential through resistance 8 is connected toterminal operation of relays 4 and 24 over a circuit as previously traced to grounded battery throughthe windings of magnets3 and 23.

T he operation of relays 4 and-24 establishes circuits through the windings o1" relays 5 120. No. 8, there will not be a shunt to prevent the and 25 in multiple extendingirom ground] through the windingsof relay 5, rightcontact ofrelay 4, brush 7, and associated ter-- minal and ground through the windings of relay 25, right contact of relay 24, brush 27 and associated terminal to the common point connected to the resistance 8 and grounded battery. Since the relays 5 and 25 are in multiple there is insuilicientcurrent flow to operate either relay and thus they remain in their normalnon-operated condition.

lVith relay Snormal and relay toperated, a circuit is established to energize relay 1 in the same manner as previously described; and further, with relay 25 normaland relay 2 L operated, a circuit is established to operate relay 21. The operationof relay 1 establishes I a circuit to energize magnet 3. The operation of magnet 3 opens the holding circuit for relay 4 which releases magnet 3 and relay 1 for the advancement of brushes 7, l2, and 13 to the next succeeding terminal in the manner previously described. The, operation of relay 21 establishes an energizing circuit for magnet 23 in the same manner as described for magnet The operation of magnet 23 opens the holding circuit for relay 24 to cause its release in the same manner as described for relay 4:. The release of relay 2% opens the energizing circuit for magnet 23 to cause its will not be propelled far before they are out of step with each other, which will allow one to select an idle terminal before the other switch arrives at that terminal. 7

Let it be assumed for the following description that two or more switches are arrested upon the multiple of the same idle trunk,

but that the brushes of one of these switches arrive at this multiple slightly before: the others. Under such a condition, relay 4: is

operatedbefore the relays, corresponding to relay 4, in the other circuits are associated with the-same terminal, and thus a circuit is established for relay'5 before it is placed in multiplewith the relays. corresponding to 5, of the other circuits. If relay alias time tooperate so that the locking circuit is estab-.

lished through its left winding to battery through resistance 8, there will be sufiicient current to hold relay 5 in an operated position, even though it were placedin mult ple with other relays, corresponding to 5, upon the operation of'relays corresponding to 4, in the other circuits. 'In tlii-snianner,'.the one hunting circuit seizes the idle trunk.

For this reason, they brushes of two switches, such as 10 and 20,

In the remainingcircuitsthat have associated their hunting brush, corresponding to brush 7,,with the idle trunk, the relays, corresponding to relays 5 or '25, remain in an unoperate'd position, .since these relays are placed in multiple' and do not receive sulficient current through their windings to cause their operation. In the hunting circuits that i have the-unoperated relays, circuits are established to energize relays, corresponding'to 21, and to energize the switch magnets, corresponding to 23, which open the holding cir-' curt for t'herezlays, corresponding to relay 24,

which further cause the release ofthe magnets, to advance the brushes of such switches in search of idle trunk circuits beyond the i one with which switch 10 is associated.

That is claimed is:

1. In a telephone exchange system, in com.- bInation, a plurality of switches, lines, a primary driving circuitffor each switch,-a primary test circuit toflcontrol said primary driving circuit for the selection of an idle line, asecondary driving circuit for each switch and a secondary test circuit to control said secondary driving circuit when more than one of said switches has selected the same idle line. 7

2. In an electrical control system, hunt-- ,ing circuits comprising a plural ty of switches with movable brushes and fixed terminals, brush driving CIICIlltS, means to brushesbecome associated with an idle terininal, means to establish second brush driving circuits when more than one brush is simultaneously associated with the same idle terminal, and means to restore 'touse said first driving circuits. in

3. Inan electrical controlsystein, hunting, circuits comprising a plurality of switches with movable brushes and fixed terminals, brush driving circuits, means to disestablish said driving circuits when said brushes become associated with an idle terminal,-means to establish second brush driving circuits when morethan one brush issimultaneously associated withthe same idle terminal, and means controlled by said second driving circuitsv to restore to use said first driving circuits. i y

4. In a {telephone exchange system, huntdisestablish said driving circuitsqwhen said i liliing circuits comprising a plurality of.

switches with movable brushes and fixed. t8I'II11niLlS,l)I'llSh driving circuits, meansfor disestablishing said xdriving circuits when said brushes become associated withian idle terminal itO arrest the movement of said .brushes,and means to -establish a seconddriv ing-circuit'forithe movement of said arrested brushes'if'morethanone brush is arrested upon the same :idle terminal, I

15. In a telephoneexchange system, in combination, incoming lines, outgoing trunks, a plurality of switches. with movable brushes lishing said driving circuits, when said brushesbecome associated with an idle 'terminal, :to arrest the movement of said brushes,{means to-prevent the connection of incoming lines to an: outgoing trunk ii the brushes of more than'one switch are arrested upon the same ldle terminal, and means to establish a second driving circuit tor the movement of said arrested brushes.

6. Ina telephone exchange system, in combination, incoming lines, outgoing trunks, a plurality of switches with movable brushes and fixed terminals for associating said incoming lines with said outgoing trunks, brush driving circuits, means for disestablishing said driving circuits, when said brushes become associated withan idle terminal to arrest the movement of said brushes, means to establish a connection from one incoming line to an outgoing trunk ii the brushes of more than one switch are arrested upon the same idle terminal, and means to establish a second driving circuitfor the movement of arrested brushes other than the one associated with the connected line.

7. In a-telephonesyste-m, in combination, a switch, lines, a' primary driving circuit, a primary test circuit to control said primary driving circuit for the selection of anidle line, a secondary driving circuit and a secondary test circuit to control said secondary driving circuit if the idle line selected is faulty.

'8. In an electrical control system, hunting circuits comprising a plurality of switches with movable brushes and fixed terminals, brush driving circuits, means to disestablish said driving circuits when said brushes become associated with an idle terminal or with a terminal which is in an unstandard 9. In atelephone exchange system, a pluralit-y of sets of stationary terminals associated with electrical apparatus, one of each set being a test terminal, a movable brush, test terminals characterized as busy, test terminals characterized as idle, test terminals connected to a faulty conductor or apparatus, means to move said brush over said stationary terminals. toselect idle terminals, means to arrest the movement of said brush upon'an idle terminal, means to arrest the movement of said brush upon a terminal connected to a faulty conductor or apparatus and means automatically operable thereupon to restart the movement of said brush in search of an idle terminal. I

10. In a telephone system, lines, fixed test terminals for said lines, a 'switch having'a driving circuit, a second test circuit made responsive to other conditions of said line upon theoperation of said first testcircuit,

and means controlled by said second test circuit for reestablishing' said driving circuits 11. Ina telephone system, lines, fixed test terminals tor said hnes, a switch having a brush adapted to engage saidterminals, driving means'ifor said switch, a test circuit responsive to one-condition of line to disable said driving means, a second test circult made responsive to otherconditions ofsaid line upon the operation'ot said first test circnit, and means controlled by said second test circuit for establishing connections to said line.

12. In a telephone system, lines, fixed test terminals for said lines, a switch having a brush adapted to engage said terminals, driving means for said switch, a driving circuit for said means, a test circuit responsive to one condition of line to disable said driving circuit, a second test circuit made responsive to other conditions of said line upon the op oration of'said first test circuit, and means controlled by said second testcircuit for reestablishing said first test circuit and said driving circuit. i

13. In a telephone system, fixed terminals associated with electrical circuits, switches having brushes adapted to engage said termi nals, driving means for said switches, a driving circuit in each switch for said means, a testing circuit for each switch including means operable in response to tests of certain conditions associated with said terminals for of said driving circuits dependent upon the action of each of said secondary testing means. I

14-. In a telephone system, fixed test terminals, a switch having a brush adapted to engage said terminals, driving means for said switch,a driving circuit fol-said switch including means for testing the condition of terminals associated-with said brush.

means responsive to certain conditions tested Y for disabling said driving circuit, means for making a supplementary test of said disabling condition, and means under the control of said secondary. testing'meains for render-mg sald driving circuit againefi'ectivel 15. In a telephone system, fixed test termi nals,a switch having abrush adapted toengage said terminals, driving means 'for said SWltCh, a drivingcircultior said switch inresponsive to certain tests to simultaneously 7 7 cluding means for testing the conditionot terminals associated with said brush, means responsive to certain tests to disable said driving means, a secondary means for testing terminals associated with said brush, and means under the control of said secondary testing means for establishing an auxiliary driving circuit for said driving means.

16, In a telephone system, fixed test terminals, a switch having a brush adapted to engage said terminals, driving means for said switch, a normal driving circuit for said switch including meansitor testing the condi tion of terminals associated with said brush, means responsive to certain tests to disable said driving means, a secondary means for testing terminals associated with said brush, means under the control of said secondary testing means for establishing an auxiliary driving circuit for said driving means, mid means for rendering said normal driving circuit again eifectivein response tot-he action ensuing from the establishment of said auxiliary driving circuit.

17. In a telephone system, fixed terminals associatedwith electrical circuits, switches, each having a brush adapted to engage said terminals, driving means for each switch, a driving circuit for each of said driving means including means for testing the condition of terminals associatedwitli each brush, means disable a plurality of said driving circuits, secondary means for testing terminals asso-, ciated with said brushes, and means under the control of each secondary testing means for rendering any of said driving circuits again efi'ect-ive.

18. In a telephone system, lines, fixedtest terminals for said lines, switches having brushes adapted to engage said terminals, driving means for said switches, test circuits responsive to any of a plurality of conditions of said lines to disable said driving means, other test circuitsmade responsive to one of said conditions of said lines, and means controlled by said second test circuit for rendering said driving means again effective.

19. In a telephone system, lines, fixed test terminals for said lines, a switch having a brush adapted to engage said terminals, driving means for said switch, a primary test circuit for energizing said driving means, a

secondary test circuit responsive to one con- I dition of a line encountered to disable said driving circuit, a tertiary test circuit made responsive to a particular condition of said line, and means controlled by said tertiary test circuit for rendering 'said primary test circuit again effective.

20. In a telephone system, banks of fixed terminals associated with electrical circuits, a plurality of switches with movable brushes, brush driving circuits, means for disabling said driving circuits responsive to the association of said brushes with certain of said electrical circuits, and second brush driving circuits independent of said firstdriving cir'- cuits automatically established for disconnecting any of said'brushes from one of said certain circuits when the brushes of more than oneswitch have been associated with the same circuit.

21. In a telephone system, lines, fixed test terminals for said lines, a switch having a brush adapted to engage said terminals, driving means for said switch, a test circuit responsive to one condition of a line to disable said driving means, a second test circuit made responsive to other conditions of said line, and means controlled by said second test circuit for either establishing connections to said line or rendering said driving means again effective depending upon the condition of said line. p

22. In a telephone system, in combination incoming lines, outgoing lines, a switch 'for interconnecting an incoming and an outgoing line, driving means for said switch, a primary test circuit including means operable upon the test of'any outgoing line for disabling said driving means, thus positioning the switch for the interconnection of an incoming line to a particular outgoing line, and a secondary test circuit, established by the operation of saidprimarytestingmeans,including means for controlling either the connection of said incoming line to said particular outgoing 1 line or for rendering said driving means. again eifective, the alternative being dependent upon difli'erent conditions established at said particular outgoing line.

In witness whereof, I hereunto subscribe myname this 31st day of March A. D., 1925. a

I EDWARDE. HINRICHSEN. 

